Photographic materials having good original reproducibility and requiring stable processing solutions or processing solutions having simplified replenishment are in demand to cope with the diversity and complexity of photomechanical printing processes.
In particular, phototypeset letters, handwritten letters, illustrations, and dotted photographs are mounted as originals and reproduced using a line camera. Accordingly, the originals have different densities and different line widths. The demand is great for process cameras, photographic materials, and image forming methods for finishing these originals with good reproducibility., In plate making, for catalogues or large-size posters, the enlargement (spread) or reduction (choke) of halftone photographs is widely carried out. In plate making using enlarged (spread) halftone dots, screen ruling becomes rough and out-of-focus dots are photographed, in plate making using choked dots, screen ruling/inch is larger than that of the original and finer dots are photographed. Thus, an image forming method useful for these situations must have a much wider latitude than is currently available to maintain the reproducibility of halftone gradation.
A halogen lamp or a xenon lamp is used as the light source for process cameras. Generally, photographic materials are subjected to ortho-sensitization so that they will be photosensitive to these light sources. However, it has been found that ortho-sensitized photographic materials are greatly affected by the chromatic aberration of lenses and as a result, the images produced with such materials are likely to be poor. Poor images are most pronounced when a xenon lamp is used as the light source.
Known systems that attempt to cope with the demand for wide latitude requirements for photochemical printing are, methods for obtaining line drawings or halftone images having a high contrast and a high blackening density wherein the image area and non-image area are clearly distinguished from each other. This is done by processing lith type silver halide photographic materials containing silver chlorobromide (having a silver chloride content of at least 50%) with hydroquinone developing solutions containing sulfite ion at a very low effective concentration (generally not higher than 0.1 mol/l). However, since the concentration of sulfite ion in the developing solution is low in these methods, the developing solution is very sensitive to air oxidation. This was necessitated a variety of additional efforts to keep the activity of the developing solution stable. These methods, unfortunately, make the processing speed very low and unfortunately, make the working efficiency low.
In view of this, there is great demand for an image forming system that is free of the problem of unstable image formation associated with the above-described developing method (lith development system). That is, a developing method that enables development to be conducted with a processing solution having good storage stability and also gives ultra-high contrast photographic characteristics is desired.
There have been proposed systems wherein surface latent image type silver halide photographic materials containing specific hydrazine compounds are processed with developing solutions having a pH of 11.0 to 12.3, (That contains sulfite preservatives in an amount of at least 0.15 mol/l and has good storage stability) to form ultra-high contrast negative images having a .gamma. (gamma) greater than 10. Such systems are described in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606, and 4,311,781. These novel systems are characterized in that silver iodobromide and silver chloroiodiobromide can be used, even though only silver chlorobromide having a high silver chloride content can be used in conventional ultra-high contrast image forming systems.
The above-described image systems give good halftone quality, processing stability, rapidness and original reproducibility. However, a large demand still exists for a system having improved original reproducibility to cope with the diversity of prints. That are currently copied using photomechanical printing processes.
JP-A-61-213847 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and U.S. Pat. No. 4,684,604 disclose photographic materials containing redox compounds which release a photographically useful group by oxidation. These patents attempt to widen the gradation reproduction region. However, the desired redox compounds interfere with high contrast in ultra-high contrast processing systems using hydrazine compounds.
Embodiments containing redox compounds which release a restrainer by oxidation in the systems using hydrazine compounds are disclosed in JP-A-61-156043, JP-A-61-213847 and JP-A-64-72140. However, when redox compounds which release a restrainer are used in systems for obtaining high contrast with hydrazine compounds, the .gamma. (gamma) value is lowered. On the other hand, when the amount of hydrazine compounds is increased, highly active hydrazine compound is used or a chemically sensitized silver halide emulsion is used, black peppers are formed.
Embodiments wherein hydroquinone derivatives are added to systems using hydrazine compounds are disclosed in JP-A-54-40629, JP-A-56-1936, JP-A-56-9743, JP-A-56-89738, JP-A-57-129436, JPA-57-129433, JP-A-57-129434, JP-A-57-129435, JP-A-61-233734, JP-A-62-247351, JP-A-63-15237, JP-A-63-103232, JP-A-01-55549, JP-A-01-147536, and JP-A-62-21143.
Embodiments using silver chlorobromide are disclosed in JP-A-53-20921, JP-A-54-37732, JP-A-60-83028, JP-A-60-112034, JP-A-62-235947, and JP-A-63-103232.